SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '257cfa98d328a706c64eff6968cf4565dd0c97f76898763d9629567839721656' 
  AND token = 'fYiMT9orL0V8z9rH8YaAs7I49BUcBURofpCshVofsx4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}